The invention relates to a twin-spool gas turbine engine with means of driving the gears of the gear box to which the accessories are fitted.
Some of the power generated by an aeronautical gas turbine engine is used to power various accessories, both of the engine and of the aircraft for which the engine provides some of the propulsive power.
Some of this power is currently tapped off the high-pressure (HP) compressor, the compressed air from which is used, in particular, to pressurize and air-condition the cabin of the aircraft or the de-icing. Another portion of this power is tapped mechanically off the shaft of the HP stage of the engine to drive the input shaft of an accessory gear box positioned on a casing of the engine. This input shaft is rotationally driven by a radial transmission shaft running through a structural arm of the intermediate casing and itself driven by a gear secured to the HP shaft.
The accessory gear box well known to those skilled in the art by its English term and abbreviation “Accessory Gear Box (AGB)” supports various machines, or accessories, for example a generator, a starter motor, an alternator, hydraulic, fuel or oil pumps, etc. These various accessories are mechanically driven by the HP shaft, via radial transmission shafts.
There is a current trend toward increasing the amount of mechanical power tapped off because of the ever increasing role played by electrical means which are held to have greater flexibility of use.
However, tapping off excessive amounts of mechanical power has a detrimental effect on the operation of the HP spool because it is liable to cause the compressor to hunt, particularly when the engine is running at low speed.